The present invention relates to data storage elements typically used in conveying apparatus for the sortation of articles and particularly to an improved data storage element and system for accurately detecting the existence of the data storage element and the data carried thereby.
In systems for the sorting and distribution of articles in a conveyor system, frequently tote pans or other article carrying devices include data storage means such as code cards which are read when the article carrier passes through a reading station. When a predetermined data code is detected, the system may divert the article at a certain discharge chute in, for example, a sorting conveyor system. Several optical, electromechanical, and magnetic code cards and reading devices are known. One problem faced by such devices is the uneven movement of a conveyor due to vibration, speed changes and other factors which can cause erroneous readings of the programmed code. U.S. Pat. No. 3,751,640 issued Aug. 7, 1973 to Daigle et al. and assigned to the present assignee discloses a code card and reading system which represents a significant improvement over existing prior art by providing a code card with selectively movable blocks positioned in rows for use with an optical reading device. Although the system disclosed therein provides accurate reading of a code, the system is designed to, in effect, look at each of the data locations of the entire card and at the same time, and thus input parallel data to the code reader. This is most economically achieved by providing, at each station, a plurality of sensors arranged in a pattern corresponding to a desired code to be read. Thus, although the system provides a greatly improved and accurate code reading arrangement it still requires that each of the sorting stations provide a unique card reading detecting arrangement and further requires a significant amount of wiring due to the utilization of a parallel code reading arrangement.
Serial code scanning systems also are known. Representative of one such system is U.S. Pat. No. 4,028,528 issued June 7, 1977 to Staes and assigned to the present assignee. In this system a single row code strip is read by at least a pair of detectors to generate clock pulses directly from the data locations of the code strip, which pulses are employed for shifting the data read into a storage device such as a shift register. Although this system provides serial scanning and therefore simplifies the data reading stations, it suggests only a two bit code which must be serially scanned and therefore requires a relatively long code carrying element. Also the clock pulses are identical to the data pulses thereby failing to provide for the analysis of detected signals possible with the present system to assure accuracy of the reading of the programmed data.